Recently, non-volatile semiconductor memory device with a ferroelectric material represented by such as lead zirconium titanate (PZT:Pb(Zr,Ti)O3), bismuth strontium tantalite (SBT:SrBi2Ta2O9) or the like as a capacitance insulator has been especially noted regarding to high speed and low consumption power.
The ferroelectric materials are metal oxides, therefore, are easily reduced by a strong reductive gas such as hydrogen or the like. As a result, the electrical characteristics are deteriorated to lower reliability of the ferroelectric capacitor. To overcome the results mentioned above, the ferroelectric capacitor is covered with an insulative hydrogen barrier film, such as an aluminum-oxide film formed by sputtering, so that the hydrogen barrier performance is improved.
However, as miniaturization of the non-volatile semiconductor memory device has proceeded, an aspect ratio of the ferroelectric capacitor has been increased to lower step coverage of the hydrogen barrier film in sputtering technology. As a result, the thickness of the hydrogen barrier film formed on the side-wall of the ferroelectric capacitor is decreased to reduce the hydrogen barrier performance.
Consequently, improvement of the step coverage on the side-wall of the ferroelectric capacitor is disclosed, for example, in Japanese Patent Publication (Kokai) No. 2003-115545.
The ferroelectric capacitor disclosed in Japanese Patent Publication (Kokai) No. 2003-115545, is stacked a lower portion electrode, the ferroelectric film and an upper portion electrode on a silicon substrate in order. Further, a Ta2O5 film is formed on the side-wall of the ferroelectric capacitor, subsequently, an Al2O3 film is formed on the Ta2O5 film by MOCVD (Metal Organic Chemical Vapor Deposition). Adhesion between the side-wall of the ferroelectric capacitor and the Al2O3 film is improved by being sandwiched the insulator such as the Ta2O5 or the like between the side-wall of the ferroelectric capacitor and the Al2O3 film, so that the step coverage with an aspect ratio being 1-2 in the side-wall of the dielectric capacitor is also improved.
However, the ferroelectric capacitor disclosed in Japanese Patent Publication (Kokai) No. 2003-115545 may be damaged in the film growth in MOCVD. Because hydrogen as a carrier gas in MOCVD or a material gas with an organic metal material is included in the processing step. Therefore, the ferroelectric film is exposed against hydrogen, even if being temporarily.